The above is an example statement, which unfortunately isn't 100% formatted as it is in SSMS. Anyway, I'll try to explain, what looks a bit odd.

USING, ON, WHEN MATCHED, WHEN NOT MATCHED are indented, whereas I would understand them to be part of the MERGE statement itself. The keywords THEN UPDATE SET and THEN INSERT are each on a new line - I understand, that it comes down to personal preferences here, but I would see UPDATE SET and INSERT as actions, whereas THEN would belong to the WHEN clause itself. The openening bracket after VALUES is on a new line, whereas the opening bracket after INSERT is on the same line as the keyword.